There is probably a small mistake from your /etc/dirvish/master.conf or in the individual default.conf files (or their location.)
Below is a copy of part of my home server's /etc/dirvish/master.conf (I've simplified the file by cutting it down to one bank and one vault.)
bank:
/backup/localhost
image-default: %m-%d-%Y-%T
log: gzip
index: gzip
xdev: 0
exclude:
lost+found/
Runall:
localhost-etc
expire-default: +20 days
image-perm: 700
meta-perm: 600
In this master.conf, I have one "bank" located at /backup/localhost. Within that one "bank", I have one "vault", called localhost-etc. (Vaults are defined under "Runall:")
For this bank and vault to be valid, I have to have a directory created at /backup/localhost/localhost-etc. Within that directory, I have another directory created, called dirvish (/backup/localhost/localhost-etc/dirvish). Within that dirvish directory, there is a default.conf file that creates the information about that vault (/backup/localhost/localhost-etc/dirvish/default.conf). This location and file is what dirvish is looking for any time I run "dirvish-runall" or "dirvish --vault localhost-etc".
Here is the contents of that default.conf
client: backup2
tree: /etc
xdev: 0
index: gzip
expire-default: +60 days
In that default.conf, that "backup2" next to client, is the name of that machine to be backed up (the local name of this machine, in this case) and you'll notice that I have "expire-default" set to a different value in that file than I have in the /etc/dirvish/master.conf that I referenced earlier. If you include something in the default.conf that you also had defined in master.conf, then the default.conf takes precedence. In my case, most of my backups are only kept for 20 days (which is what I defined in master.conf). I decided that I wanted to keep the localhost-etc backups for 60 days, though, so I included that in the default.conf.
Hope that helps. Let me know if you need any more help with dirvish.
Chris